Epoxy a 1/4 inch piece of hardwood the same width of the beam to he bottom of the beam full length. Inset the engine lugs on the top of the original beams till the bottom of the lugs are flush with the top of the original beams. Mount the engine with the top of the lugs down. be sure the bottom of your insets are exactly parallel with each other, and you can't rock the engine. Don't do this if the lug tops are not straight and flat.